均三甲苯在MCM-22和MCM-56分子筛上的吸附和扩散

Adsorption and diffusion of mesitylene on MCM-22 and MCM-56 molecular sieves

以MCM-22和MCM-56分子筛为研究对象,考察烃类均三甲苯在MWW型分子筛上的吸附和扩散,同时对分子筛进行XRD、N2吸附和TEM等表征,探究分子筛的结构特性与吸附和扩散之间的关系。研究表明,均三甲苯在MWW型分子筛中的吸附和扩散位置为外表面半超笼。单层和错层结构使MCM-56较MCM-22分子筛拥有更多的外表面酸性位,有利于均三甲苯的吸附。与MCM-22相比,MCM-56分子筛片层结构较薄,焙烧导致晶体外部结构的卷曲使烃类大分子均三甲苯在MCM-56分子筛中的扩散受阻。

Using the adsorption and diffusion of large molecular hydrocarbon mesitylene in MWW type molecular sieves as the probe, the properties of MCM-22 and MCM-56 molecular sieves were studied. The molecUlar sieves were characterized by the techniques of XRD, N2 adsorption and TEM in order to investigate the relationship between the structure of molecular sieves and adsorption and diffusion. The results showed that the adsorption and diffusion of mesitylene were in the external surface （ external cups） of MWW-type molecular sieves. MCM-56 molecular sieve possessed more acid sites in its external surface than MCM-22 molecular sieve due to its monolayer structure and staggered layer structure. Compared with MCM-22 molecular sieve ,more acid site and curled surface of MCM-56 molecular sieve after calcination prevented mesitylene from diffusion on the molecular sieve.